Bugfix: Incorrect documentation and fix return types in f_file_stream_write functions.

Bugfix: Incorrect documentation and fix return types in f_file_stream_write functions.

Clean up the logic and make it less redundant.
Move the return state logic into the private method.

This allows the reduction of some variables.
This allows the reduction of code.

This is now returning `F_okay_eos` or `F_okay_stop` when it should.
There is no `F_okay_eof` being returned.

Documentation comments are now correct and consistent.